Presently there has become a renewed interest in the Stirling engine particularly with regard to its use in varying applications. A basic Stirling engine design, particularly with regard to the well known free-piston Stirling engine for example, involves the cycle of compressing a gas enclosed in a chamber at a low temperature and transporting or conveying the gas to a high temperature working chamber with the gas being heated and allowed to expand, with such expansion resulting in the generation of mechanical work. The gas is then transferred back to the low temperature chamber and the cycle repeats. In such a free-piston design, the expanding gas pressure wave deflects a mechanical device such as a flexible diaphragm or bellow which in turn displaces hydraulic fluid which in turn may be used to displace a piston. The displacement of the piston is in the form of mechanical work and can be used for a multitude of purposes, which in the present application would be to provide power for hydraulic pumping.
Heretofore, there has been provided a pumping unit for hydraulic fluid for use in conjunction with a Stirling engine which utilizes the energy existing in its cycle. However, such pumping units tended to upset the balancing and synchronization of operation of the engine or are otherwise undesirable for reasons particular to their application.